Ok, this has worked for me in the past, but depending on your windows setup, it may not work:
Turn on your PC and when you get to the screen where it shows the Windows logo and that little green bar is going from left to right, left to right, left to right, hold down your power button until it shuts down.
Next, boot up again, and it will say your PC was unexpectedly shut down then ask if you want to boot into safe mode, say yes.
You will now see you are in Windows, if the login pops up, then stop because this method won't work for you.
Go to Start -> Control Panel -> User Accounts -> (Your Acount) -> Reset Password
You won't be able to see the password it was set at before, but now you can change it to something new.
Good luck,
airhendrix13